Separation media could be for example chromatography media and density gradient media. The media could be for example resins based on natural or synthetic polymer particles or inorganic material. For chromatography the separation media needs to be provided into a chromatography column. For the transportation of the separation media into for example a column the media needs first to be suspended into an homogenous media slurry mixture. The separation media is normally suspended with a liquid, for example water, buffer or a solvent. This suspended media is usually called media slurry. When a column should be filled with media slurry from a storage container, an intermediate tank is used where the slurry is mixed into a homogenous mixture. The media slurry is often stirred manually in the tank and it is important that the media slurry becomes a homogenous mixture regarding the distribution of different sizes of particles in the media. Of course it is not convenient to stir manually especially when there is a large amount of media slurry to be stirred. It could also take quite a long time to fill the column with the media slurry and the media slurry needs to be stirred the whole time. Another way to mix the slurry that is sometimes used is to shake or tilt the tank back and forth. This could be advantageous for small tanks and small volumes of slurry but is hard to perform and not suitable for big, heavy tanks.
Solutions have been proposed, for example in EP0515955 or JP4323557, where permanent, electrical stirrers, also called impellers are used. There are however different problems associated with these kind of impellers. If the impeller is not running the whole time when the media slurry is inside the tank the slurry will sediment and then it will be hard to start the impeller in the sedimented media. This requires furthermore an oversized engine. When starting the impeller in sedimented media the media particles can be damaged because of shear forces provided by the impeller. It could be preferable to not run the impeller the whole time in order to minimize possible damage to the particles caused by the impeller.